1. Field of the Invention
The present invention relates to computer networks. More particularly, the present invention relates to a method and system for managing communication in a computer network using aliases of computer network addresses.
2. Background Information
To access information on the Internet and, more particularly, the World Wide Web (WWW), users access websites that offer information and/or services. The information and/or services offered by a website are stored in and provided by computer network servers that are generally located remotely from the user. As the number of Internet users grow, computer network servers can experience an increase in the number of connections from clients to access the information and/or services available on these websites. To handle the increased connection load, the computer network servers can be scaled to meet the increased demand. For example, computer network servers can be replicated and the server replicas can be clustered to meet the increased demand. Thus, as the client connection load increases, more servers can be replicated and clustered. Because of their scalability and flexibility, computer network server clusters have become a popular method of meeting increasing communications traffic demands.
Computer network servers based on clusters of workstations or personal computers (PCs) generally include a specialized “front-end” device that is responsible for distributing incoming requests from clients to one of a number of “back-end” nodes, where the “back-end” nodes are responsible for processing the incoming requests from the clients. The front-end is responsible for handing off new connections and passing incoming data from the client to the back-end nodes. In cluster server architectures, the front-end can use weighted round-robin request distribution to direct incoming requests to the back-end nodes. With weighted round-robin distribution, incoming requests are distributed in round-robin fashion and are weighted by some measure of the load on the different back-ends.
To distribute the communications traffic among the back-end nodes, the front-end acts as a load balancer that attempts to evenly distribute the communications traffic load from the clients among the available back-end nodes. A load balancer can be, for example, a switch that connects the servers to the clients for whom the information and/or services are to be provided. To meet increasing connection loads, the load balancers can be upgraded with faster computer processors and more internal computer memory. To further increase performance and improve connection distribution among the back-end nodes, the front-end can use, for example, the content requested, in addition to information about the load on the back-end nodes, to choose which back-end server will handle a particular request.
Content-based request distribution is discussed in, for example, “Locality-Aware Request Distribution in Cluster-Based Network Servers,” by Vivek S. Pai, et al. (Proceedings of the ACM Eighth International Conference on Architectural Support for Programming Languages and Operating Systems (ASPLOS-VIII), October 1998), the disclosure of which is incorporated herein by reference in its entirety. However, current load balancers (e.g., front-end switches) do not use the resources offered by the back-end server nodes, which are typically faster and more powerful than the load balancers, to assist the load balancer in determining the distribution of the connections among the back-end nodes. Rather, current load balancers determine request distribution autonomously from the back-end nodes.
One example of a conventional load balancer that can act as a front-end for a computer network cluster is a Layer Four (L4) switch. A L4 switch takes into account Transport Layer information (i.e., Layer Four of the International Organization for Standardization (ISO) Networking model, or ISO model). A discussion of computer network protocols and layers of the ISO model is discussed, for example, in “Interconnections, Second Edition,” by Radia Perlman (Addison-Wesley, 2000), the disclosure of which is incorporated herein by reference in its entirety. L4 switches manipulate both the network and transport protocol headers of the communications traffic passing through them to forward the communications traffic to the back-end nodes. A L4 switch can operate with, for example, the Internet Protocol (IP) for the network layer and the Transport Control Protocol (TCP) for the transport layer.
To communicate information between the back-end servers and the switch, the switch inspects the destination address to determine how to forward the packet. For example, the switch can forward the packet out every port, except the port on which the packet came. However, the packet also carries a source address. When a packet arrives on a first port of the switch, the switch can store information regarding the direction from which the packet came. When future packets are received at the switch which include that source address as the destination address, the switch can use the stored information to send the packet out on the first port, rather than flooding the packets to all ports.
When the address of a first server is to be communicated to a second server for the purpose of communicating packets between the two servers, the first server can, for example, transmit a packet to the second server that contains the address of the first server. When a first switch receives the packet, the first switch can rewrite the source address of the first server with its own address. However, this can result in the loss of the Ethernet (Medium Access Control (MAC)) address of the first server, which is the information that is to be communicated to the second server. Alternatively, the switch can leave the source address of the first server intact. However, any other switches along the path to the second server will then incorrectly learn the switch port of the first server, as opposed to the port of the first switch. This can result in packets destined for the first server being forwarded down a wrong path and possibly being lost.